1. Field of the Invention
The present invention relates to a process cartridge detachably mountable to an electrophotographic image forming apparatus such as an electrophotographic copying machine and an electrophotographic printer.
Here, the electrophotographic image forming apparatus forms an image on a recording sheet using an electrophotographic image forming method, and examples of the electrophotographic image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (for example, a laser beam printer and an LED printer), a facsimile machine and a word processor.
Furthermore, a process cartridge is a cartridge into which at least one of a charging member, a developing unit and a cleaning unit, and an electrophotographic photosensitive member are integrally incorporated, the cartridge being detachably mountable to a main body of an image forming apparatus.
2. Description of the Related Art
Conventionally, as an electrophotographic image forming apparatus, there is a color electrophotograpic image forming apparatus of an in-line type in which a plurality of process cartridges are aligned. There is a contact development method of performing a development in the state in which a developing roller forming a process cartridge is in contact with a photosensitive drum. In this method, in order to keep a predetermined contact pressure between the developing roller and the photosensitive drum during image formation, the developing roller is urged against the photosensitive drum.
In the case of this method, when the process cartridge is not used for a long time period in the state of being mounted on the image forming apparatus main body, there is a possibility that an elastic layer of the developing roller is permanently deformed. Therefore, an uneven image may be formed at the time of development.
As a result, there was proposed a process cartridge and an image forming apparatus in which there is provided a mechanism for separating the developing roller from a photosensitive drum in the case of performing no image forming operation (Japanese Patent No. 2900530 (which is matured from Japanese Patent Application Laid-Open No. H04-43378) and Japanese Patent Application Laid-open No. 2001-337511).
In addition, the construction in which a charging roller serving as a charging member is abutted on a photosensitive drum for charging the photosensitive drum is widely used. In such a contact charging mechanism, since the charging roller needs to be disposed reliably in contact with the photosensitive drum surface, the charging roller is in pressure contact with the photosensitive drum surface at a predetermined contact pressure. When the state of not being used for a long time period continues, the elastic layer of the charging roller is permanently deformed, and thus, an image of uneven density is formed.
Thus, there has been proposed a method in which an insert member for separating the charging roller from the photosensitive drum is inserted therebetween at the time of shipment of a process cartridge, and a user removes the insert member in use (Japanese Patent Application Laid-Open No. H05-188667).
Alternatively, there has been proposed a process cartridge having a mechanism in which a charging roller, having been separated during shipment is brought into abutment with the photosensitive drum when the process cartridge is mounted on the image forming apparatus main body (Japanese Patent Application Laid-Open No. H06-273987 and Japanese Patent Application Laid-Open No. 2000-181328).